1. Field of the Invention
The present invention relates to a light generating device and a method of manufacturing the light generating device, more specifically to a light generating device with semiconductor and a method of manufacturing the light generating device.
2. Discussion of the Background
In general, a light generating device such as a light emitting diode (LED) has merits such as high efficiency, long lifetime, a low power consumption, eco friendliness, etc., so that the light generating device is employed in various fields.
The light generating device may be divided into two types of a lateral type and a vertical type according to a shape. According to the lateral type light generating device, an n-type semiconductor layer is formed on a substrate, and a quantum well layer (or active layer) and a p-type semiconductor layer are formed in sequence. Then, a portion of the p-type semiconductor layer and the quantum well layer is removed to expose the n-type semiconductor layer, and a p-type electrode is formed on the p-type semiconductor layer and an n-type electrode is formed on an exposed region of the n-type semiconductor layer.
The vertical type LED (or VLED) has merits such as effective heat dissipation, high electro optical characteristics to appeal, but still it is essential to enhance to light extracting efficiency for high efficiency VLED for a lighting apparatus.
The external quantum efficiency of LED is determined by multiplying internal quantum efficiency with light extracting efficiency, and the internal quantum efficiency is determined by current injection efficiency. Therefore, in order to enhance efficiency of LED, effective current distribution from an electrode to a semiconductor layer and effective injection of carrier to a quantum well layer are required.
Further, when light generated from the quantum well layer is emitted outside, a portion of the light is totally reflected due to a difference of refractive index between air and semiconductor material to lower efficiency. In order to solve the problem, roughness may be formed on a top surface of LED, or transparent and conductive material such as ITO is applied to an n-type electrode to enhance efficiency.
However, thermal damage may be generated in a high temperature process of n-type electrode of LED so that there is limitation if electrode research for high efficiency. The above problems induce low efficiency of LED. Therefore, still many researches are performed to enhance efficiency of LED.
A conventional VLED will be described in detail referring to FIG. 1.
FIG. 1 is a cross-sectional view showing a conventional VLED.
Referring to FIG. 1, a conventional vertical type LED (VLED) includes a substrate 110, a p-type electrode 120, a p-type semiconductor layer 130, an active layer 140, an n-type semiconductor layer 140 and an n-type electrode 160 in sequence. Light L generated in the active layer 140 and advance vertically upward is reflected by the n-type electrode 160 to advance downward. The light advancing downward is reflected by the substrate 110 to advance upward, so that the light L advanced upward and downward repeatedly to be attenuated. Therefore, the n-type electrode 160 makes a light loss by the about of area of the n-type electrode 160 in the total area of the VLED. Additionally, the p-type electrode 120 has substantially the same as the active layer 140 in area, and holes are uniformly provided from the p-type electrode 120 to the active layer 140 but the current I (in detail, electrons) cannot be uniformly provided to the active layer 140 from the n-type electrode 160. Therefore, only a portion of the active layer 140 generates light to reduce efficiency.